A seat reclining apparatus for adjusting an angle of a seat back of a vehicle seat requires functionality: to finely adjust the angle of the seat back so that an occupant can have an appropriate posture for driving the vehicle; to change the angle of the seat back backward by a large angle so that an occupant can use the seat like a bed, and to change the angle of the seat back forward by a large angle so that an occupant of the vehicle can get into/out of a rear seat of the vehicle with two doors. In particular, it takes a long time to fold the seat back forward when getting in or out of the vehicle from the rear seat and it would be inconvenient if the only mechanism provided to fold the seat is one that electrically and steplessly adjusts the angle of the seat back. Therefore, the seat reclining apparatus requires a mechanism for folding the seat back.
According to JPS62-224310A, to overcome the problems described above, a seat reclining apparatus conventionally includes a stepless adjustment mechanism configured from a planetary gear mechanism including a combination of a gear fixed to a seat back side and a gear fixed to a seat cushion side. A gear tooth portion is provided at an outer side of the seat back side or the seat cushion side of the planetary gear mechanism. A stopper member for engaging with the gear tooth portion is further provided. The stopper member is operated to engage/disengage by an operational lever. Then, the seat back can be laid backward or forward.
However, according to the conventional technique described above, one gear of the planetary gear mechanism and a mechanism relating to the operational lever are arranged side by side at an oblong base plate provided at the seat cushion. Further, the stopper member is provided adjacent to the planetary gear on the same plane thereof. Then, when the operational lever is operated, the stopper member is moved to engage to/disengage from the gear tooth portion (outer gear tooth) formed along periphery of the planetary gear. Then, the angle of the seat back can be roughly adjusted. Therefore, an area of the reclining apparatus seen from the side of the seat reclining apparatus becomes a sum of an area of the planetary gear and that of the stopper member. Accordingly, a size of the seat reclining apparatus tends to be made too large for a limited space in which the seat reclining apparatus should be installed. In addition to that, a design of the seat reclining apparatus tends to be degraded, and costs for manufacturing the seat tend to become higher because a size of a resin cover for covering the mechanism or the number of covers required is increased.
A need thus exists for a seat reclining apparatus, which is compact and enables to finely and roughly adjust an angle of a seat back.